Common rail direct fuel injection is a direct fuel injection system for gasoline and diesel engines in various applications, such as in providing power to machines and vehicle. In diesel engines for example, a common rail fuel injection system may feature a high-pressure fuel rail having a plurality of fuel lines each feeding an individual accumulator assembly with a valve to provide the high-pressure fuel to a corresponding fuel injector for one of the combustion cylinders of the engine. FIG. 1 illustrates an example of a known engine assembly 10 with an accumulator assembly 12 that will be inserted into a cylinder head 14. The accumulator assembly 12 includes an accumulator body 16, a fuel line adapter 18 and an accumulator clamp 20. The accumulator body 16 is generally cylindrical with an accumulator body longitudinal axis 22 and an accumulator body outer surface 24 defining a series of body sections 26, 28, 30, 32 with an accumulator body outer diameter increasing as the accumulator body 16 extends from an injector interface end 34 toward the fuel line adapter 18 and the accumulator clamp 20.
The cylinder head 14 shown in cross-section includes an accumulator bore surface 40 defining an accumulator bore 42 extending inwardly into the cylinder head 14 from an accumulator bore opening 44 in a cylinder head outer surface 46. The accumulator bore 42 has a shape that is complimentary to a shape of the accumulator body 16 with a series of bore sections 48, 50, 52, 54 corresponding to the body sections 26, 28, 30, 32, respectively, and having an accumulator bore inner diameter that increases relative to an accumulator bore longitudinal axis 56. The cylinder head 14 may further include a drain passage 58 connecting a drain port 60 of the cylinder head 14 to the accumulator bore 42. The accumulator bore surface 40 intersects a fuel injector bore surface 62 defining a fuel injector bore 64 extending inwardly into the cylinder head 14 from an injector bore opening 66 in the cylinder head outer surface 46 at a bore intersection area 68.
The accumulator body 16 is inserted into the accumulator bore 42 until the injector interface end 34 reaches the bore intersection area 68 (FIG. 2). A fuel injector 70 (FIG. 3) is installed in the injector bore 64 before the accumulator body 16 is inserted. The fuel injector 70 has a high pressure fluid inlet port 72 that is aligned at the bore intersection area 68 and approximately aligned with the accumulator bore longitudinal axis 56. When the accumulator body 16 is inserted into the accumulator bore 42, the injector interface end 34 enters the bore intersection area 68 and is received by the high pressure fluid inlet port 72 of the fuel injector 70. The injector interface end 34 and the high pressure fluid inlet port 72 have complimentary shapes so that the end 34 is guided into the port 72 and a seal is formed there between. High pressure fluid is provide through an accumulator body bore 74 to a high pressure fluid supply port 76 of the accumulator body 16 at the end 34 and to a high pressure fuel passage 78 of the fuel injector 70. The accumulator body outer diameter at each of the body sections 26, 28, 30, 32 is less than the accumulator bore inner diameter at the corresponding bore sections 48, 50, 52, 54, respectively, so that an annular gap 80 between the accumulator body outer surface 24 and the accumulator bore surface 40 is present when the injector interface end 34 is received by the high pressure fluid inlet port 72. The annular gap 80 allows cooling fluid to flow back from the fuel injector bore 64 through a cooling fluid port (not shown) at the bore intersection area 68, through the annular gap 80 in the direction indicated by arrows 82, and out of the cylinder head 14 through the drain passage 58 and the drain port 60.